When you want to show some social sharing options or introduce some other CTA buttons that re stuck to the left border of the screen this pure CSS snippet by Håvard Brynjulfsen might come in handy. We have four icons on the left border and when you hover over them they slide out and fill up with colour, moving the mouse away from it will slide in back to the corner.
If you are having trouble with the pen, try the archived copy on GitHub
Corner Buttons Snippet
See the Pen Floating social icon buttons | CSS Only by Håvard Brynjulfsen (@havardob) on CodePen.0